1. Field of the Invention
The present invention relates to an input system with detection of coordinates and particularly to an input system, in which current produces an induced magnetic field and the induced magnetic field is transformed to induced voltage for finding out corresponding positions of coordinates.
2. Description of Related Art
Generally, there are two types of coordinates input systems, touch type and non-touch type available on the market.
The touch type coordinates input system as shown in FIG. 1 usually has a touch panel, which provides a circuit plane fully distributed with conductor loci, and an electric field of alternate current is arranged on the circuit plane. Hence, a corresponding curve of induced current can be generated once the magnetic coil of an oscillation source induces the circuit plane. Then, a scanning circuit is used to detect the induced current in the conductor loci to find a spot in the conductor loci, which provides the maximum induced current according to the principle of magnitude of induced current being proportional to the intensity of magnetic field. The maximum induced current is treated with an amplifying circuit and processed by an analog/digital converter (A/D) so that the coordinates along X-axis and along Y-axis can be obtained. Although the contact type coordinates input system has advantages such as simple operation and easy controlled circuit, shortcomings such as the mechanical device thereof easily becoming fatigued, deformed and fractured, the electronic switch thereof generating sparks and noise signal during power being on, and moisture and oil vapor easily seeping into the system are subjects worth us to overcome. A typical contact type coordinate input system is resistance type coordinates input system.
The non-touch type coordinates input system typically is capacitance type or inductance type coordinates input system. Similarly, the non-contact type coordinates input system has deficiencies such as complicated circuit, high production cost, interference resulting from noise signal being unable to be removed easily and occurring phenomena such as trembling input and unstable state of coordinates input.